Heating and cooling unit for extruders and the like



J. J. FINN Nov. 15, 1966 HEATING AND COOLING UNIT FOR EXTRUDERS AND THE LIKE Filed Sept. 24, 1964 7 a j H United States Patent 3,285,329 HEATING AND COOLING UNIT FOR EXTRUDERS AND THE LIKE John J. Finn, Erie, Pa., assignor of one-half to Glenn Electric Heater Corporation, Erie, Pa., a corporation of Pennsylvania Filed Sept. 24, 1964, Ser. No. 398,854 Claims. (Cl. 165-61) In extruders for thermoplastics, it has been difficult to control the temperature of the barrel of pla-sticizing chamber. Initially, the chamber may require substantial heat but as the operation continues, the internal friction of the plastic may supply enough of the heat required so that the heating source must be quickly cut off and cooling supplied.

This invention solves the problem by units clamped onto the barrel or plasticizing chamber of an extruder which contain electric heating elements and associated cooling coils by means of which the heat input may be controlled so as to prevent excessive temperature and consequent degradation of the plastic. The construction is such that series and parallel connections of the heating elements and cooling coils may conveniently be made as desired.

In the drawing, FIG. 1 is a side elevation, :partly in section, of the barrel of an ext-ruder, FIG. 2 is an end view of one of the heating and cooling units, FIG. 3 is a bottom view of the unit, FIG. 4 is a side view of the unit, FIG. 5 is a developed view of one of the electric heating elements, FIG. 6 is a developed view of one of the cooling coils, FIG. 7 is a section through one of the segments of the unit, and FIG. 8 is a top view of the unit.

In a preferred form, 1 diagrammatically indicates the barrel and 2 the feed screw of an extruder for thermoplastics. Clamped on the barrel are a plurality of heating and cooling units 3 having cooling coils 4 connected by tubes 5 and having heating elements connected by wiring 6. The heating elements are arranged so that the wiring 6 extends axially along the length of the barrel at the top of the barrel and the cooling coils are arranged so that the connections between the cooling coils extend axially along the sides of the barrel. This physically separates the plumbing and wiring in different regions for ease of installation and maintenance.

The units have a plurality of segmental metal heat transfer members 7, 7a in end to end relation and having arcuate internal or inner surfaces 8, 8a clamped against the outer surface of the barrel 1 by clamping bands 9, 9a respectively having one end fixed to brackets 10, 10a fixed to the members 7, 7a and having the other end looped over clamping bars 11, 11a tightened by screws 12. In addition to anchoring the ends of the clamping bands 9, 9a to the metal members 7, 7a, the brackets 10, 10a support outlet boxes 13 for the electrical wiring.

The segmental members 7, 7a have in their external or outer surfaces a plurality of pairs of outwardly open circuimferentially extending grooves 14, 15, 16 in nested relation to each other. Each of the grooves as shown in FIG. 7 has its lower end of circular cross section encom-passing sufiiciently more than 180 degree-s so as to provide detent shoulders 17. A sheathed heating element 18 of the loop configuration shown in FIG. 5 is snapped into each pair of grooves 14, 1'6 and is yieldably held in the grooves by the detent shoulders 17. A cooling coil 22 of the loop configuration shown in FIG. 6 is similarly snapped into each pair of the grooves 15.

The heating element-s 18 in grooves 14 have adjacent terminals 19 between the brackets 10, 10a at one end of the grooves which may be connected in series or in parallel. The heating elements 20 in grooves 16 have similar terminals 21 which likewise may be connected in series or parallel. This permits use of the heating elements on a Wide variety of operating voltages. The terminals 19 and 21 are between the brackets 10 and 10a and are enclosed by the outlet "box 13. The cooling coil tubing 22 received in grooves 15 has ends 23 intermediate the ends of the grooves 15 and extending out through a slot 24 in the clamping band 9 or 9a, as the case may be.

While the grooves 14 and 16 are each connected at one end by a single arcuate section 24a, 25, both ends of the grooves 15 are connected by an arcuate section 26 to accommodate the cooling coil shape illustrated in FIG. 6.

The units are held in tight contact with the outer surface of the barrel 1 by the clamping bands 9, 9a which have a smaller coeflicient of expansion than the segmental units 7, 7a and the barrel so that tight contact is maintained at all operating temperatures.

At the start of the operation of the extruder, the heating elements bring the barrel and the plastic therein quickly up to extruding temperature. To prevent degradation of the plastic, it is important that the safe extruding temperature of the plastic not be exceeded. The internal friction of the plastic causes the feed screw 2 to contribute materially to the maintenance of the plastic temperature. Even if the heating elements 18, 20 were shut off completely when the proper plastic temperature was reached, there would be danger of overshoot due to heat storage in the barrel and in the sheathed heating elements and in the metal members 7, 7a. This unwanted overshoot is prevented by circulating coolant through the tubing 22, thereby quickly cooling the metal members '7, 7a and dissipating or intercepting heat from the heating elements 18, 20 before it gets a chance to be transmitted through the barrel 1 to the plastic. The direct relationship of the cooling coils 22 and the heating elements 18 and 20 is important in preventing excessive temperatures. The cooling coils 22 are also in good heat conducting relation to the barrel 1 and may be used exclusively to control the plastic temperature whenever the internal friction of the plastic generates more heat than required to maintain the extruding temperature.

The arrangement of the units 3 is such that repair and replacement is readily made. If one of the cooling coils 22 should become clogged and require replacement, it can be bypassed by making suitable changes in the connections 5 and replaced at some convenient time. Simila-r changes may be made in the wiring in case of injury to either of the heating elements 18 or 20. By having a plurality of heating and cooling units 3 distributed along the length of the barrel, it is extremely unlike-1y that all will require repair or replacement at the same time and the down time of the extruding machine can accordingly be kept to a minimum.

What is claimed as new is:

1. A heating and cooling member having arcuate segmental metal parts arranged end to end, a clamping band encircling said parts to clamp the same against a cylindrical surface, said parts having internal cylindrical surfaces and having external surfaces with at least two outwardly open circumferentially extending grooves spaced from each other, a sheathed electric heating element in one of the grooves, and a cooling coil in the other of said grooves.

2. A plasticizing chamber for an extruder having a barrel with a feed screw, a plurality of heating and cooling members embracing and distributed along the length of the barrel, each member having arcuate segmental metal parts with internalsu-rfaces engaging the external surfaces of the barrel and having external surfaces remote from the barrel, means for clamping'the metal parts against the barrel, said parts having in their external surfaces pairs of external outwardly open circumferentia-lly extending grooves in nested relation to each other, one pair of grooves having an arcuate connection section at one end, another pair of grooves having an arcuate connecting section at both ends, a sheathed electric heating element in said one pair of grooves with the terminals opposite the arcuate connecting section, and a cooling coil in said other pair of grooves with the ends between the arcuate connecting sections, the terminals of said members being aligned along one section of the barrel and the ends of the cooling coil being aligned along another section of the barrel.

3. A plasticized chamber for an extruder having a barrel with a feed screw, a plurality of heating and cooling members embracing and distributed along the length of the barrel, each member having arcuate segmental metal parts with internal surfaces engaging the external surfaces of the barrel and having external surfaces remote from the barrel, a clamping band encircling the parts of each member to clamp the same against the barrel, said parts having in their external surfaces pairs of external outwardly open circum-ferentially extending grooves in nested relation to each other, a sheathed electric heating element in the form of a first loop with sides in one of the said pairs of grooves and with terminals at the end-s of the first loop adjacent each other, and a cooling coil in the form of a second loop with sides in another of said pairs of grooves and with the ends of the second loop adjacent each other and intermediate the ends of one of the grooves of said other pair of grooves.

4. A heating and cooling member arcuate having segmental metal parts arranged end to end, a clamping band encircling said parts to clamp the same against a cylindrical surface, said .parts having internal cylindrical surfaces and having external surfaces with pairs of external circumferentially extending grooves in nested relation to each other, one pair of grooves having an arcuate connecting section at one end, another pair of grooves having an arcuate connecting section at both ends, a sheathed electric heating element in said one pair of grooves with the terminals opposite the arcuate connecting section, and a cooling coil in said other pair of grooves with the ends between the arcuate connecting sections.

5. A heating and cooling member having arcuate segmental metal parts arranged end to end, a clamping band encircling said parts to clamp the same against a cylindrical surface, said parts having internal cylindrical surfaces and having external surfaces with pairs of external outwardly open circumferentially extending grooves in nested relation to each other, a sheathed electric heating element in the form of a first loop with sides in One of said pairs of grooves and with terminals at the ends of the first loop adjacent each other, and a cooling coil in the form of a second loop with sides in another of said pairs of grooves and with the ends of the second loop adjacent each other and intermediate the ends of one of the grooves of said other pair of grooves.

References Cited by the Examiner UNITED STATES PATENTS 2,522,365 9/1950 Greene 18-12 2,541,201 2/1951 Buecken et a1. 18-12 2,549,569 4/1951 Bradley 18-12 2,832,879 4/1958 Van Riper 18-12 3,055,053 9/1962 Livingston et a1. l812 3,167,812 2/1965 Bennigsen 18--l2 ROBERT A. OLEARY, Primary Examiner.

T. W. STREULE, JR., Assistant Examiner. 

1. A HEATING AND COOLING MEMBER HAVING ARCUATE SEGMENTAL METAL PARTS ARRANGED END TO END, A CLAMPING BAND ENCIRCLING SAID PARTS TO CLAMP THE SAME AGAINST A CYLINDRICAL SURFACES, SAID PARTS HAVING INTERNAL CYLINDRICAL SURFACES AND HAVING EXTERNAL SURFACES WITH AT LEAST TWO OUTWARDLY OPEN CIRCUMFERENTIALLY EXTENDING GROOVES SPACED FROM EACH OTHER, A SHEATHED ELECTRIC HEATING ELEMENT IN ONE OF THE GROOVES, AND A COOLING COIL IN THE OTHER OF SAID GROOVES. 